/*
 * CKFinder
 * ========
 * http://cksource.com/ckfinder
 * Copyright (C) 2007-2015, CKSource - Frederico Knabben. All rights reserved.
 *
 * The software, this file and its contents are subject to the CKFinder
 * License. Please read the license.txt file before using, installing, copying,
 * modifying or distribute this file or part of its contents. The contents of
 * this file is part of the Source Code of CKFinder.
 */
package com.ckfinder.connector;

import java.io.IOException;
import java.util.HashSet;

import javax.servlet.ServletConfig;
import javax.servlet.ServletContext;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import com.ckfinder.connector.configuration.Configuration;
import com.ckfinder.connector.configuration.ConfigurationFactory;
import com.ckfinder.connector.configuration.Constants;
import com.ckfinder.connector.configuration.Events.EventTypes;
import com.ckfinder.connector.configuration.IConfiguration;
import com.ckfinder.connector.data.BeforeExecuteCommandEventArgs;
import com.ckfinder.connector.errors.ConnectorException;
import com.ckfinder.connector.handlers.command.Command;
import com.ckfinder.connector.handlers.command.CopyFilesCommand;
import com.ckfinder.connector.handlers.command.CreateFolderCommand;
import com.ckfinder.connector.handlers.command.DeleteFilesCommand;
import com.ckfinder.connector.handlers.command.DeleteFolderCommand;
import com.ckfinder.connector.handlers.command.DownloadFileCommand;
import com.ckfinder.connector.handlers.command.ErrorCommand;
import com.ckfinder.connector.handlers.command.FileUploadCommand;
import com.ckfinder.connector.handlers.command.GetFilesCommand;
import com.ckfinder.connector.handlers.command.GetFoldersCommand;
import com.ckfinder.connector.handlers.command.IPostCommand;
import com.ckfinder.connector.handlers.command.InitCommand;
import com.ckfinder.connector.handlers.command.MoveFilesCommand;
import com.ckfinder.connector.handlers.command.QuickUploadCommand;
import com.ckfinder.connector.handlers.command.RenameFileCommand;
import com.ckfinder.connector.handlers.command.RenameFolderCommand;
import com.ckfinder.connector.handlers.command.ThumbnailCommand;
import com.ckfinder.connector.handlers.command.XMLCommand;
import com.ckfinder.connector.handlers.command.XMLErrorCommand;
import com.ckfinder.connector.utils.AccessControlUtil;
import java.util.logging.Level;
import java.util.logging.Logger;

/**
 * Main connector servlet for handling CKFinder requests.
 */
public class ConnectorServlet extends HttpServlet {

	/**
	 * holds exception if any occurs during CKFinder start.
	 */
	private Exception startException;
	/**
	 */
	private static final long serialVersionUID = 2960665641425153638L;

	/**
	 * Handling get requests.
	 *
	 * @param request request
	 * @param response response
	 * @throws IOException .
	 * @throws ServletException .
	 */
	@Override
	protected void doGet(final HttpServletRequest request,
		final HttpServletResponse response) throws ServletException,
		IOException {
		request.setCharacterEncoding("UTF-8");
		response.setCharacterEncoding("UTF-8");
		getResponse(request, response, false);
	}

	/**
	 * Handling post requests.
	 *
	 * @param request request
	 * @param response response
	 * @throws IOException .
	 * @throws ServletException .
	 */
	@Override
	protected void doPost(final HttpServletRequest request,
		final HttpServletResponse response) throws ServletException,
		IOException {
		request.setCharacterEncoding("UTF-8");
		response.setCharacterEncoding("UTF-8");
		getResponse(request, response, true);
	}

	/**
	 * Creating response for every command in request parameter.
	 *
	 * @param request request
	 * @param response response
	 * @param post if it's post command.
	 * @throws ServletException when error occurs.
	 */
	private void getResponse(final HttpServletRequest request,
		final HttpServletResponse response, final boolean post)
		throws ServletException {
		if (startException != null
			&& Boolean.valueOf(getServletConfig().getInitParameter("debug"))) {
			throw new ServletException(startException);
		}
		boolean isNativeCommand;
		String command = request.getParameter("command");
		IConfiguration configuration = null;
		try {
			configuration = ConfigurationFactory.getInstace().getConfiguration(request);
			if (configuration == null) {
				throw new Exception("Configuration wasn't initialized correctly. Check server logs.");
			}
		} catch (Exception e) {
			if (Boolean.valueOf(getServletConfig().getInitParameter("debug"))) {
				Logger.getLogger(ConnectorServlet.class.getName()).log(Level.SEVERE, "Configuration wasn't initialized correctly. Check server logs.", e);
			}
			throw new ServletException(e);
		}
		try {

			if (command == null || command.equals("")) {
				throw new ConnectorException(
					Constants.Errors.CKFINDER_CONNECTOR_ERROR_INVALID_COMMAND, false);
			}

			configuration.setDebugMode(
				Boolean.valueOf(getServletConfig().getInitParameter("debug")));

			if (CommandHandlerEnum.contains(command.toUpperCase())) {
				CommandHandlerEnum cmd;
				isNativeCommand = true;
				cmd = CommandHandlerEnum.valueOf(command.toUpperCase());
				// checks if command should go via POST request or it's a post request
				// and it's not upload command
				if ((cmd.getCommand() instanceof IPostCommand || post)
					&& !CommandHandlerEnum.FILEUPLOAD.equals(cmd)
					&& !CommandHandlerEnum.QUICKUPLOAD.equals(cmd)) {
					checkPostRequest(request);
				}
			} else {
				isNativeCommand = false;
			}

			BeforeExecuteCommandEventArgs args = new BeforeExecuteCommandEventArgs();
			args.setCommand(command);
			args.setRequest(request);
			args.setResponse(response);

			if (configuration.getEvents() != null) {
				if (configuration.getEvents().run(EventTypes.BeforeExecuteCommand,
					args, configuration)) {
					if (!isNativeCommand) {
						command = null;
					}
					executeNativeCommand(command, request, response, configuration, isNativeCommand);
				}
			} else {
				if (!isNativeCommand) {
					command = null;
				}
				executeNativeCommand(command, request, response, configuration, isNativeCommand);
			}
		} catch (IllegalArgumentException e) {
			if (Boolean.valueOf(getServletConfig().getInitParameter("debug"))) {
				Logger.getLogger(ConnectorServlet.class.getName()).log(Level.SEVERE, "Couldn't execute native command.", e);
				response.reset();
				throw new ServletException(e);
			} else {
				handleError(
					new ConnectorException(
						Constants.Errors.CKFINDER_CONNECTOR_ERROR_INVALID_COMMAND, false),
					configuration, request, response, command);
			}
		} catch (ConnectorException e) {
			if (Boolean.valueOf(getServletConfig().getInitParameter("debug"))) {
				Logger.getLogger(ConnectorServlet.class.getName()).log(Level.SEVERE,
					e.getErrorMessage(), e.getException() != null ? e.getException() : e);
				response.reset();
				throw new ServletException(e.getException());
			} else {
				handleError(e, configuration, request, response, command);
			}
		}
	}

	/**
	 * Executes one of connector's predefined commands specified as parameter.
	 *
	 * @param command string representing command name
	 * @param request current request object
	 * @param respose current response object
	 * @param configuration CKFinder connector configuration
	 * @param isNativeCommand flag indicating whether command is available in enumeration object
	 *
	 * @throws ConnectorException when command isn't native
	 * @throws IllegalArgumentException when provided command is not found in enumeration object
	 */
	private void executeNativeCommand(String command, final HttpServletRequest request,
		final HttpServletResponse response, IConfiguration configuration,
		boolean isNativeCommand) throws IllegalArgumentException, ConnectorException {
		if (isNativeCommand) {
			CommandHandlerEnum cmd = CommandHandlerEnum.valueOf(command.toUpperCase());
			cmd.execute(
				request, response, configuration, getServletContext());
		} else {
			throw new ConnectorException(
				Constants.Errors.CKFINDER_CONNECTOR_ERROR_INVALID_COMMAND, false);
		}
	}

	/**
	 * checks post request if it's ckfinder command.
	 *
	 * @param request request
	 * @throws ConnectorException when param isn't set or has wrong value.
	 */
	private void checkPostRequest(final HttpServletRequest request)
		throws ConnectorException {
		if (request.getParameter("CKFinderCommand") == null
			|| !(request.getParameter("CKFinderCommand").equals("true"))) {
			throw new ConnectorException(
				Constants.Errors.CKFINDER_CONNECTOR_ERROR_INVALID_REQUEST, true);
		}

	}

	/**
	 * handles error from execute command.
	 *
	 * @param e exception
	 * @param request request
	 * @param response response
	 * @param configuration connector configuration
	 * @param currentCommand current command
	 * @throws ServletException when error handling fails.
	 */
	private void handleError(final ConnectorException e,
		final IConfiguration configuration,
		final HttpServletRequest request, final HttpServletResponse response,
		final String currentCommand)
		throws ServletException {
		try {
			if (currentCommand != null && !currentCommand.equals("")) {
				Command command = CommandHandlerEnum.valueOf(
					currentCommand.toUpperCase()).getCommand();
				if (command instanceof XMLCommand) {
					CommandHandlerEnum.XMLERROR.execute(request, response, configuration,
						getServletContext(), e);
				} else {
					CommandHandlerEnum.ERROR.execute(request, response, configuration,
						getServletContext(), e);
				}
			} else {
				CommandHandlerEnum.XMLERROR.execute(request, response, configuration,
					getServletContext(), e);
			}

		} catch (Exception e1) {
			throw new ServletException(e1);
		}
	}

	@Override
	@SuppressWarnings("UseSpecificCatch")
	public void init() throws ServletException {
		ServletContextFactory.setServletContext(getServletContext());
		IConfiguration configuration;
		try {
			String className = getServletConfig().getInitParameter(
				"configuration");
			if (className != null) {
				Class<?> clazz = Class.forName(className);

				if (clazz.getConstructor(ServletConfig.class) != null) {
					configuration = (IConfiguration) clazz.getConstructor(
						ServletConfig.class).newInstance(getServletConfig());

				} else {
					configuration = (IConfiguration) clazz.newInstance();
				}
			} else {
				configuration = new Configuration(getServletConfig());
			}
		} catch (Exception e) {
			Logger.getLogger(ConnectorServlet.class.getName()).log(Level.SEVERE,
				"Couldn't initialize custom configuration. Rolling back to the default one.", e);
			configuration = new Configuration(getServletConfig());
		}
		try {
			configuration.init();
			AccessControlUtil.getInstance().loadConfiguration(configuration);
		} catch (Exception e) {
			if (Boolean.valueOf(getServletConfig().getInitParameter("debug"))) {
				Logger.getLogger(ConnectorServlet.class.getName()).log(Level.SEVERE, "Couldn't initialize configuration object.", e);
			}
			this.startException = e;
			configuration = null;
		}
		ConfigurationFactory.getInstace().setConfiguration(configuration);
	}

	/**
	 * Enum with all command handles by servlet.
	 *
	 */
	private enum CommandHandlerEnum {

		/**
		 * init command.
		 */
		INIT(new InitCommand()),
		/**
		 * get subfolders for selected location command.
		 */
		GETFOLDERS(new GetFoldersCommand()),
		/**
		 * get files from current folder command.
		 */
		GETFILES(new GetFilesCommand()),
		/**
		 * get thumbnail for file command.
		 */
		THUMBNAIL(new ThumbnailCommand()),
		/**
		 * download file command.
		 */
		DOWNLOADFILE(new DownloadFileCommand()),
		/**
		 * create subfolder.
		 */
		CREATEFOLDER(new CreateFolderCommand()),
		/**
		 * rename file.
		 */
		RENAMEFILE(new RenameFileCommand()),
		/**
		 * rename folder.
		 */
		RENAMEFOLDER(new RenameFolderCommand()),
		/**
		 * delete folder.
		 */
		DELETEFOLDER(new DeleteFolderCommand()),
		/**
		 * copy files.
		 */
		COPYFILES(new CopyFilesCommand()),
		/**
		 * move files.
		 */
		MOVEFILES(new MoveFilesCommand()),
		/**
		 * delete files.
		 */
		DELETEFILES(new DeleteFilesCommand()),
		/**
		 * file upload.
		 */
		FILEUPLOAD(new FileUploadCommand()),
		/**
		 * quick file upload.
		 */
		QUICKUPLOAD(new QuickUploadCommand()),
		/**
		 * XML error command.
		 */
		XMLERROR(new XMLErrorCommand()),
		/**
		 * error command.
		 */
		ERROR(new ErrorCommand());
		/**
		 * command class for enum field.
		 */
		private Command command;
		/**
		 * {@code Set} holding enumeration values,
		 */
		private static final HashSet<String> enumValues = new HashSet<String>();

		/**
		 * Enum constructor to set command.
		 *
		 * @param command1 command name
		 */
		private CommandHandlerEnum(final Command command1) {
			this.command = command1;
		}

		/**
		 * Fills in {@code Set} holding enumeration values for this {@code Enum}.
		 */
		private static void setEnums() {
			for (CommandHandlerEnum enumValue : CommandHandlerEnum.values()) {
				enumValues.add(enumValue.name());
			}
		}

		/**
		 * Checks whether enumeration object contains command name specified as parameter.
		 *
		 * @param enumValue string representing command name to check
		 *
		 * @return {@code true} is command exists, {@code false} otherwise
		 */
		public static boolean contains(String enumValue) {
			if (enumValues.isEmpty()) {
				setEnums();
			}
			for (String value : enumValues) {
				if (value.equals(enumValue)) {
					return true;
				}
			}
			return false;
		}

		/**
		 * Executes command.
		 *
		 * @param request request
		 * @param response response
		 * @param configuration connector configuration
		 * @param sc servletContext
		 * @param params params for command.
		 * @throws ConnectorException when error occurs
		 */
		private void execute(final HttpServletRequest request,
			final HttpServletResponse response, final IConfiguration configuration,
			final ServletContext sc, final Object... params)
			throws ConnectorException {
			Command com = null;
			try {
				com = command.getClass().newInstance();
			} catch (IllegalAccessException e1) {
				throw new ConnectorException(
					Constants.Errors.CKFINDER_CONNECTOR_ERROR_INVALID_COMMAND);
			} catch (InstantiationException e1) {
				throw new ConnectorException(
					Constants.Errors.CKFINDER_CONNECTOR_ERROR_INVALID_COMMAND);
			}
			if (com == null) {
				throw new ConnectorException(
					Constants.Errors.CKFINDER_CONNECTOR_ERROR_INVALID_COMMAND);
			}
			com.runCommand(request, response, configuration, params);
		}

		/**
		 * gets command.
		 *
		 * @return command
		 */
		public Command getCommand() {
			return this.command;
		}
	}
}
